Facilities for U-Pb Geochronology at The University of Texas at Austin

The U-Pb geochronology laboratory at The University of Texas at Austin follow most of the methods developed by Tom Krogh of the Royal Ontario Museum, Toronto, Ontario, Canada. We employ standard mineral separation techniques (crusher, disc mill pulverizer, Wilfley table, sieves, heavy liquids and Frantz magnetic separators). We analyze the minimum amount of material possible for each sample without unnecessarily compromising analytical precision. Every grain analyzed is carefully selected from a bulk separate using a picking microscope, scrutinized under transmitting light microscope, re-picked to exclude inclusions invisible to the standard picking microscope and then extensively air abraded prior to dissolution. We also utilize cathodolumescence to image the internal structures of minerals to better characterize and understand mineral populations before analyses. In the clean laboratory, we use a mixed Pb205-U235 tracer, dissolve and separate U and Pb using standard anion-exchange separation techniques. We typically run U and Pb on a single Re filament on our up-graded Finnigan-MAT 261 multicollector with an axial secondary electron multiplier - ion counting system. Our total procedural blanks are routinely less than 1 pg and .25 pg for Pb and U respectively. Our data is reduced, plotted and regressed using a locally developed (and freely available) software package that is based on algorithms from the Royal Ontario Museum, Toronto, Canada.

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Chris McFarlane operates the Finnigan-MAT 261 thermal ionization mass spectrometer. 

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